WTF Just Happened: My New HDTV Makes Movies Look Unnaturally Smooth

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WTF Just Happened: My New HDTV Makes Movies Look Unnaturally Smooth

Jim Merithew/WIRED

You just bought a brand-new TV, but instead of being blown away by the picture you’re starting to think it actually makes everything look worse. Well, maybe worse is the wrong word. Unnaturally smooth is more like it. Movies don’t look like movies; they look like they were shot on a camcorder. Why is your TV fixing what ain't broke?

This annoying little phenomenon is commonly referred to as the "soap opera effect," and it's a byproduct of your TV's motion-enhancing features. Thankfully, the effect can be turned off, and that's probably a good idea when you're watching movies. While these smoothing features can make a few things look better—scrolling tickers, sports, and HDTV test discs, for example—our eyes and brains expect something very different when we’re watching movies. A slower frame rate is one of them.

Nearly every motion picture since the dawn of talkies has been shot at a frame rate of 24fps (24p), a standard that has survived the film-to-digital transition. Many TV shows are shot at 24fps nowadays. But that 24fps rate is at odds with the way TV stations broadcast content and the way TVs display that content. Right off the bat, 24p film or video has to be modified a bit to display properly when it's broadcast.

For broadcast TV, video is delivered to your set at a rate of 60 "fields" per second. One field can represent an interlaced mash-up of two frames so that motion appears more fluid. Until recently, all TVs had a standard refresh rate of 60Hz to match up perfectly with the rate at which that stream feeds into your set. But newer LCD/LED sets often advertise a 120Hz or 240Hz refresh rate to help combat motion blur (more on that in a bit).

With 24p content, the film has to be scanned or the digital video has to be modified to look right on TV. That’s because 24 frames don’t fit evenly into those 60 fields. With 30p content, the frames can be interlaced to create a 60i stream or displayed twice each to achieve the 60-fields-per-second rate. But if 24fps content were played at 30fps, the on-screen motion would appear 25 percent faster—and if the audio kept pace, everyone would sound like a helium addict. If frames were dropped to 20fps, which fits more nicely into 60, the video would look too choppy. So instead, every four frames of 24p source content is turned into five frames using a process called 2:3 pulldown.

When this modified video is viewed on a TV, the content has been adjusted by creating two interlaced fields that combine adjacent frames in every five-field batch. It essentially turns 24p video into 30fps video, which is more compatible with the way TVs and broadcast systems work.

None of that is what causes the distracting too-smooth effect. However, it does mean that 24p content broadcast on TV already looks a bit different from what the director intended. What really takes it into soap-opera land is when a modern set’s motion-smoothing features are enabled.

If you bought a mid- to high-end LED/LCD TV in the last few years, it certainly has these features built in. I’m focusing on LED/LCD sets here, because plasma sets are all but dead and OLED sets are still rare. LED/LCD TVs often have these motion features due to the panel technology’s traditional problems with motion blur.

If your set is a 120Hz or 240Hz one, it adds faux frames to source content if motion-smoothing settings are turned on. The higher refresh rate means the panel can show many more new images per second—even if those images aren’t in the original content—in order to make everything look more smooth. These additional frames are completely made-up: There’s enough processing power in a modern TV to analyze successive frames, create fake “interpolated” frames that split the difference between them, and display them between real frames.

So let’s say you’re watching a movie on cable with all your TV’s motion-fanciness settings turned on. In this scenario, you’re watching a movie that started out at 24fps, was modified with hybrid frames to make it more broadcast-friendly, and is now at the point where there may be more fake frames than real frames in what you’re watching. Depending on your TV’s refresh rate and the frame rate of the source content, these motion features can add two to four times as many frames to the original video.

But just as a 120Hz or 240Hz TV can make movies look less like movies, it can also be the ultimate screen for watching 24p content as intended. If you’re watching a movie on Blu-ray, make sure your Blu-ray player is set to a 24p output mode and all those motion settings are turned off on your TV. This should make your TV show each frame of your 24p content 5 times per second on a 120Hz set or 10 times per second on a 240Hz TV. As for the other aesthetic qualities of watching movies on TV, using the set's Movie mode, Cinema mode, Film mode, or THX mode (if your set has it) usually works best.